package com.sylar.lelepub.widget;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

public class ScrollLayout extends ViewGroup {

	private Scroller mScroller;
	private VelocityTracker mVelocityTracker;
	private int mCurScreen;
	private int mDefaultScreen = 0;
	private static final int TOUCH_STATE_REST = 0;
	private static final int TOUCH_STATE_SCROLLING = 1;
	private static final int SNAP_VELOCITY = 500;
	private int mTouchState = TOUCH_STATE_REST;
	private int mTouchSlop;
	private float mLastMotionX;
	private int sensitivity = 30;
	private boolean spring;

	private ScrollLayoutChange viewChangeListener;
	
	public ScrollLayout(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		mScroller = new Scroller(context);
		mCurScreen = mDefaultScreen;
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
	}


	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		// TODO Auto-generated method stub
		int childLeft = 0;
		final int childCount = getChildCount();
		for (int i = 0; i < childCount; i++) {
			final View childView = getChildAt(i);
			if (childView.getVisibility() != View.GONE) {
				final int childWidth = childView.getMeasuredWidth();
				childView.layout(childLeft, 0, childLeft + childWidth,
						childView.getMeasuredHeight());
				childLeft += childWidth;
			}
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		final int width = MeasureSpec.getSize(widthMeasureSpec);
		final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		if (widthMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException(
					"ScrollLayout only canmCurScreen run at EXACTLY mode!");
		}

		final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
		if (heightMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException(
					"ScrollLayout only can run at EXACTLY mode!");
		}

		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
		}
		scrollTo(mCurScreen * width, 0);
	}

	public void snapToDestination() {
		final int screenWidth = getWidth();
		final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
		snapToScreen(destScreen);
	}

	public void snapToScreen(int whichScreen) {
		// get the valid layout page
		int lastIndex = mCurScreen;
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		if (getScrollX() != (whichScreen * getWidth())) {

			final int delta = whichScreen * getWidth() - getScrollX();
			mScroller.startScroll(getScrollX(), 0, delta, 0,
					Math.abs(delta) * 2);
			mCurScreen = whichScreen;
			invalidate(); // Redraw the layout
		}
		
		if(viewChangeListener!=null)
			viewChangeListener.onViewChange(mCurScreen);
	}

	public void setOnViewChangeListener(ScrollLayoutChange listener){
		this.viewChangeListener = listener;
	}
	
	public interface ScrollLayoutChange{
		void onViewChange(int curScreen);
	}
	
	public void setToScreen(int whichScreen) {
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		mCurScreen = whichScreen;
		scrollTo(whichScreen * getWidth(), 0);
	}

	public int getCurScreen() {
		return mCurScreen;
	}

	@Override
	public void computeScroll() {
		// TODO Auto-generated method stub
		if (mScroller.computeScrollOffset()) {
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			postInvalidate();
		}
	}

	public boolean isSpring() {
		return spring;
	}

	public void setSpring(boolean spring) {
		this.spring = spring;
	}

//	@Override
//	public boolean onTouchEvent(MotionEvent event) {
//		// TODO Auto-generated method stub
//		if (mVelocityTracker == null)
//			mVelocityTracker = VelocityTracker.obtain();
//		mVelocityTracker.addMovement(event);
//		final int action = event.getAction();
//		final float x = event.getX();
//		switch (action) {
//		case MotionEvent.ACTION_DOWN:
//			if (!mScroller.isFinished())
//				mScroller.abortAnimation();
//			mLastMotionX = x;
//			break;
//		case MotionEvent.ACTION_MOVE:
//			int deltaX = (int) (mLastMotionX - x);
//			if (Math.abs(deltaX) > sensitivity) {
//				if (spring) {
//					scrollBy(deltaX, 0);
//					mLastMotionX = x;
//				} else {
//					final int childCount = getChildCount();
//					boolean max = mCurScreen < childCount - 1;
//					boolean min = mCurScreen > 0;
//					boolean canMove = deltaX > 0 ? (max ? true : false)
//							: (min ? true : false);
//					if (canMove) {
//						scrollBy(deltaX, 0);
//						mLastMotionX = x;
//					}
//				}
//			}
//			break;
//		case MotionEvent.ACTION_UP:
//			final VelocityTracker velocityTracker = mVelocityTracker;
//			velocityTracker.computeCurrentVelocity(1000);
//			int velocityX = (int) velocityTracker.getXVelocity();
//			if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
//				// Fling enough to move left
//				snapToScreen(mCurScreen - 1);
//			} else if (velocityX < -SNAP_VELOCITY
//					&& mCurScreen < getChildCount() - 1) {
//				// Fling enough to move right
//				snapToScreen(mCurScreen + 1);
//			} else {
//				snapToDestination();
//			}
//			if (mVelocityTracker != null) {
//				mVelocityTracker.recycle();
//				mVelocityTracker = null;
//			}
//			mTouchState = TOUCH_STATE_REST;
//			break;
//		case MotionEvent.ACTION_CANCEL:
//			mTouchState = TOUCH_STATE_REST;
//			break;
//		}
//		return true;
//	}
//
//	@Override
//	public boolean onInterceptTouchEvent(MotionEvent ev) {
//		// TODO Auto-generated method stub
//		final int action = ev.getAction();
//		if ((action == MotionEvent.ACTION_MOVE)
//				&& (mTouchState != TOUCH_STATE_REST))
//			return true;
//		final float x = ev.getX();
//		switch (action) {
//		case MotionEvent.ACTION_MOVE:
//			final int xDiff = (int) Math.abs(mLastMotionX - x);
//			if (xDiff > mTouchSlop)
//				mTouchState = TOUCH_STATE_SCROLLING;
//			break;
//		case MotionEvent.ACTION_DOWN:
//			mLastMotionX = x;
//			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
//					: TOUCH_STATE_SCROLLING;
//			break;
//		case MotionEvent.ACTION_CANCEL:
//		case MotionEvent.ACTION_UP:
//			mTouchState = TOUCH_STATE_REST;
//			break;
//		}
//		return mTouchState != TOUCH_STATE_REST;
//	}

}